The ordinary example of the conventional forklift controller has a configuration wherein the output shaft of the engine and the wheel are connected via a stagged transmission having a sliding factor. A loading driving actuator of the lift cylinder is connected to the output shaft of the engine via a fixed pump. In addition, this controller is equipped with an accelerator pedal directly connected to the throttle valve of the engine and a clutch pedal (for a forklift truck with an automatic transmission, this is referred to as an inching pedal) as an interconnection means of the wheel to the output shaft of the engine through operation of the sliding factor, thus adjusting the vehicle speed and loading speed via these two (2) pedals. Specifically, only during a loading operation in a stopped position, the loading speed is adjusted by an amount of depression of the accelerator pedal when the clutch is released. Also, the vehicle speed is adjusted by the amount of depression of the accelerator pedal only when running/moving after the loading operation at a stopped position when the clutch pedal is connected.
However, with this type of forklift, in many cases, the vehicle body is moving at a desirable speed when the lift is elevated, that is, moving while loaded. The forklift equipped with the conventional controller adjusts both the vehicle speed and loading speed through the stepping action (depression) on the accelerator pedal. Thus, it is impossible to independently operate only the vehicle speed or number of revolutions of the engine. Therefore, an operator has no method to get a desirable vehicle speed and loading speed other than searching for a balanced point of both speeds of the accelerator and clutch through simultaneous operation thereof. Thus, the conventional forklift has problems because operation for proper loading while running is difficult and a higher level of skill is required for the operator.
Some conventional forklifts wherein the vehicle speed control had been controlled from the standpoint of improvement of the operation ability have been known. However, no forklifts wherein the fuel consumption factor had been considered existed. That is, in the conventional forklift as mentioned above, the target value of the vehicle speed is set depending on the amount of depression of the accelerator pedal. The accelerator is depressed and then its operating amount is conveyed to the throttle valve via wires. Thus, immediately after the throttle valve is closed and the engine is accelerated, only the speed ratio of the transmission is changed upward to the motive power transmission status where the vehicle speed obtains a target value to the number of revolutions of the engine. Therefore, the number of revolutions of the engine increases as the opening of the throttle increases. However, one of the engine characteristics is that the target number of revolutions of the engine also has an optimum fuel consumption for the throttle opening. The conventional forklift has a problem that as the number of revolutions of the engine actually increases, and thus changes with no relation to the optimum fuel consumption conditions, the fuel consumption rate worsens and a great deal of loss occurs during full operation.